From patchwork Tue May 14 01:13:27 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mat Martineau X-Patchwork-Id: 13663748 X-Patchwork-Delegate: mat@martineau.name Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B1CFD524F; Tue, 14 May 2024 01:13:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715649222; cv=none; b=tWEDYFFm9+BukaE/n0WW5hZUkQvPovwe4Qgc186xOQvUKt8z6rF3+DRhbsS9KPyICTv6TVyHt0n572dy46AiEHlSMPWV5C8c9D3Eal7usSFRuc6BJJYEwR2mqFtO94L4PUW0kAvGAJtgWhwNScmJRxcqTliZ6QesRNdCdEEkncE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715649222; c=relaxed/simple; bh=n9oAOoyV8ndvOD7gMvnNfgAjFUhX65q5z8LOi/+KKtA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TdzVNJ/v3YHh/2EVLi85hBLN7uLKsDu/66XdpZkGO9vfGpRZ39tVTaan4yG/+iAki+oWyzqEGo9nd+fgNpmzTqONjjTcJGHSmxtb8BWga/XZY7DaxN3N83JT2S3UdZekuDWhzJnLqebyV5vf502XPt8OszoS29uIQiKrCn+9oNk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=J8TQ0hv3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="J8TQ0hv3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED80EC4AF16; Tue, 14 May 2024 01:13:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715649222; bh=n9oAOoyV8ndvOD7gMvnNfgAjFUhX65q5z8LOi/+KKtA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J8TQ0hv3qmDmHOXYFKYTx13UHkszIygak84lQNDzNrM/dc6SP3HnYA6njG4VZRfzC tKsW+oYDccMGeQkbe8v3pHu2f5bOPYrp5LiSVB5NzOMicLlcsl5oFRGBZ+iRk3wDLJ SK3/1SKVbqIcjlr2Ek4ZS81G6lNSc87hXnSRWGpUMOuuNlWnqTtlJvWqQDUkaCG2ZK jvN6rSR9U8DFMQur1q529k6GvjyMrt3mMy9MI1Q6/EAy3L66FeCmBjqpKdeHQBozko 4fZWfYo1dnocZQMb9h78D/9/31klxVP1Juh977AZGpwWBIzjW0gjPLRFYlu/dvHbxg w1Kosq5cdbU/w== From: Mat Martineau To: mptcp@lists.linux.dev, geliang@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, fw@strlen.de Cc: "Matthieu Baerts (NGI0)" , netdev@vger.kernel.org, Mat Martineau Subject: [PATCH net-next v2 3/8] mptcp: sockopt: info: stop early if no buffer Date: Mon, 13 May 2024 18:13:27 -0700 Message-ID: <20240514011335.176158-4-martineau@kernel.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240514011335.176158-1-martineau@kernel.org> References: <20240514011335.176158-1-martineau@kernel.org> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Matthieu Baerts (NGI0)" Up to recently, it has been recommended to use getsockopt(MPTCP_INFO) to check if a fallback to TCP happened, or if the client requested to use MPTCP. In this case, the userspace app is only interested by the returned value of the getsocktop() call, and can then give 0 for the option length, and NULL for the buffer address. An easy optimisation is then to stop early, and avoid filling a local buffer -- which now requires two different locks -- if it is not needed. Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Mat Martineau --- net/mptcp/sockopt.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index fcca9433c858..a77b33488176 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -999,6 +999,10 @@ static int mptcp_getsockopt_info(struct mptcp_sock *msk, char __user *optval, in if (get_user(len, optlen)) return -EFAULT; + /* When used only to check if a fallback to TCP happened. */ + if (len == 0) + return 0; + len = min_t(unsigned int, len, sizeof(struct mptcp_info)); mptcp_diag_fill_info(msk, &m_info);